Ken Olson: Livestock water quality in wet years
July 8, 2011
Recently I have read some articles in the beef press about toxicity issues in livestock drinking water. The articles were from the Southern Plains where they have severe drought. They discuss sulfate, nitrate and blue-green algae issues. We typically think of these as drought issues, but they can also be serious problems in wet years. I want to discuss the wet year issues since that is what most everyone is dealing with in the Northern Plains.
Many producers in the Northern Plains dealt with serious sulfate toxicity issues during the droughty years of the early 2000s. In general, this is a drought issue because the sulfate content in a pond or dam or even in shallow ground water (including springs and wells) will become more concentrated as the level of water declines. Think of it as a distillation process; evaporation of water will lead to increased concentration of all components that can’t evaporate.
However, there are cases when sulfate can increase in a pond as it fills in a wet year. If there is high sulfate in the soils and parent material of the watershed upstream of a pond, that sulfate will be picked up by runoff and flow into the pond. These sulfates are usually, but not always, dilute because plenty of water filled the pond. However, there are cases where sulfate content can rise as fast or faster than the rising water level. Ponds that you suspect or have tested in the drought years and know are sources of high sulfate should still be treated with caution.
Nitrate is also soluble and will be picked up and flow with runoff into a pond, or into the recharge area for a spring or well. The place to be concerned about this is if the water source is downstream of a crop field that was fertilized with nitrogen. I have recently seen a press release where crops specialists were telling farmers to be concerned that there is less nitrogen for their crops than they think because it ran off with the heavy rains many have experienced. If it ran off the field, it flowed somewhere downstream, and that could be into a stock pond, spring, or well. Nitrate toxicity concerns will be the same as for high nitrate forages. Again, we often think of high-nitrate forages as a drought concern, but in this case in water, it is more of a concern in wet years.
Finally, blue-green algae blooms can be a problem in wet years. Basically, blue-green algae shows up in late summer as pond scum that is blue, green, red, or purple in color. Two things promote it: hot temperatures and high nutrient levels in the water. High nutrient levels is the result of high levels of nitrogen or phosphorous flowing into the pond or other water source from manure or fertilizer. Again, just like the toxicity of the nitrate itself that ran off of fertilized fields, the secondary toxic effect could be an algae bloom later in the summer if it gets hot. There is evidence that treating ponds with copper sulfate will kill blue-green algae. However, it takes at least two weeks for the process to reach the point that the toxicity has been eliminated. Some evidence suggests that the algae blooms are usually transient and will go away on their own in the same time frame.
I suggest that everyone keep an eye on their livestock water sources this summer looking for the potential for any of these three issues. If you see the potential, it would be wise to send a sample to a lab for analysis. Unfortunately, if toxic levels are present, we don’t have antidotes for any of these issues. It simply means the livestock need to be provided alternative water or moved to a different pasture. Despite the fact that these are not the best solutions, they are better than allowing livestock losses to occur.